En:Sonic and some portions of the genesis consoleSonic 1: Eggman and his robotsSonic 2: Tails (The poor tails was added in the last minute XD)Sonic 3: Knuckles (look the background, you can see the Death Egg)Sonic & Knuckles: Mecha Sonic

I agree, SEGA should've put more classic into Generations. There were only 3 levels which originally come from the classic games, the other six are from the modern ones. And why on earth did they not allow Classic Sonic to talk?!! Not only that it makes no sense as Classic Tails can talk (and he's younger than Sonic!!), it also made Modern Sonic the leader and degraded Classic Sonic to just a sidekick. I love Generations, but the balance between classic and modern could definitely been better.